Yeah, I think the helper classes and the settings in Style Settings > Minimal Cards are the only tweaks you can do without CSS.
For the horizontal table borders, you could play around with this. I’d try with border: or border-top: as well depending on what you’re going for.
.markdown-source-view.mod-cm6.cards table.dataview tbody > tr > td {
border-bottom: .05px solid red; }
As for the right side vertical line, I don’t see that. Could be some other conflicting CSS or a plugin? I’d have a look in the inspector to see where it’s coming from:
